This invention relates to swinging devices, and finds particular utility in connection with children's devices, such as cradles and swings. In general, however, the invention is applicable to swinging devices of any description.
Power-driven swings are desirable in such applications as infant swings and cradles for keeping the infant amused or contented while leaving the parent free for other chores. Such mechanisms are not without their disadvantages, however, notably their susceptibility to jamming or slamming of parts resulting in unpleasant and sometimes dangerous jolts to the occupant. Jolts and jerky movements also occur during startup and shutdown, or when the cycle of the swing is interrupted to permit removal of the occupant. Frequently such mechanisms necessitate manual assistance for startup due to the mechanism's inability to transmit sufficient torque to overcome the gravitational load of the static mechanism. All this can be particularly troublesome when an infant is placed in the swing, since it may frighten the infant or cause injury.
It has now been discovered that much if not all of this difficulty is eliminated by a drive mechanism in which an extension spring joins the suspension arm of the swing to a gear wheel coupled to a rotating drive shaft of an electric motor through meshed gears. Circular rotation of the gear wheel is translated to linear oscillation of the force exerted on the extension spring which, combined with the spring's resilient character, provides a smooth swinging motion. The configurations of various embodiments of the invention allow the spring(s) to flex and bow permitting the interruption, start or stop of either the motor or swing in any position without damage to the motor or drive mechanism, followed by subsequent unassisted startup or smooth continuation of the swinging cycle when the motor is energized. The cycle may thus be frequently started or stopped by a timer or other automatic control mechanism, thereby further enhancing the application of the invention. Additionally, the configuration of various embodiments permits the use of a control circuit whereby the speed of the motor, under various loads, can be monitored and the electrical power input to the motor adjusted thereby maximizing efficiency and minimizing power consumption. The gear wheel, drive shaft speed, and any intermediate gears are sized and selected to conform to the period of the swing's oscillation.
Among the various embodiments of the invention, the gear wheel may be coupled to the drive shaft through either a worm gear or a spur gear on the drive shaft, either directly or through reduction gears. In further embodiments, two gear wheels are included, each linked to a separate extension spring, with the two springs applying pull forces to the swing in alternating manner and in opposite directions. The two gear wheels are either in mesh with each other or both in mesh with a worm gear on the drive shaft to produce rotation in opposite directions.
Further embodiments will be evident from the description which follows.